/* $OpenBSD: position.c,v 1.11 2019/06/28 13:34:59 deraadt Exp $ */ /* $NetBSD: position.c,v 1.4 1995/03/21 09:04:12 cgd Exp $ */ /*- * Copyright (c) 1991, 1993, 1994 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Keith Muller of the University of California, San Diego and Lance * Visser of Convex Computer Corporation. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include #include #include #include #include #include #include #include #include #include "dd.h" #include "extern.h" /* * Position input/output data streams before starting the copy. Device type * dependent. Seekable devices use lseek, and the rest position by reading. * Seeking past the end of file can cause null blocks to be written to the * output. */ void pos_in(void) { size_t bcnt; ssize_t nr; off_t cnt; int warned; /* If not a pipe, tape or tty device, try to seek on it. */ if (!(in.flags & (ISPIPE|ISTAPE)) && !isatty(in.fd)) { if (lseek(in.fd, in.offset * in.dbsz, SEEK_CUR) == -1) err(1, "%s", in.name); return; } /* * Read the data. If a pipe, read until satisfy the number of bytes * being skipped. No differentiation for reading complete and partial * blocks for other devices. */ for (bcnt = in.dbsz, cnt = in.offset, warned = 0; cnt;) { if ((nr = read(in.fd, in.db, bcnt)) > 0) { if (in.flags & ISPIPE) { if (!(bcnt -= nr)) { bcnt = in.dbsz; --cnt; } } else --cnt; continue; } if (nr == 0) { if (files_cnt > 1) { --files_cnt; continue; } errx(1, "skip reached end of input"); } /* * Input error -- either EOF with no more files, or I/O error. * If noerror not set die. POSIX requires that the warning * message be followed by an I/O display. */ if (ddflags & C_NOERROR) { if (!warned) { warn("%s", in.name); warned = 1; summary(); } continue; } err(1, "%s", in.name); } } void pos_out(void) { struct mtop t_op; off_t cnt; ssize_t n; /* * If not a tape, try seeking on the file. Seeking on a pipe is * going to fail, but don't protect the user -- they shouldn't * have specified the seek operand. */ if (!(out.flags & ISTAPE)) { if (lseek(out.fd, out.offset * out.dbsz, SEEK_SET) == -1) err(1, "%s", out.name); return; } /* If no read access, try using mtio. */ if (out.flags & NOREAD) { t_op.mt_op = MTFSR; t_op.mt_count = out.offset; if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) err(1, "%s", out.name); return; } /* Read it. */ for (cnt = 0; cnt < out.offset; ++cnt) { if ((n = read(out.fd, out.db, out.dbsz)) > 0) continue; if (n == -1) err(1, "%s", out.name); /* * If reach EOF, fill with NUL characters; first, back up over * the EOF mark. Note, cnt has not yet been incremented, so * the EOF read does not count as a seek'd block. */ t_op.mt_op = MTBSR; t_op.mt_count = 1; if (ioctl(out.fd, MTIOCTOP, &t_op) == -1) err(1, "%s", out.name); while (cnt++ < out.offset) if ((n = write(out.fd, out.db, out.dbsz)) != out.dbsz) err(1, "%s", out.name); break; } }